Americans United for Separation of Church and State sued state officials last year in federal court, claiming the government was endorsing Christianity by approving the plates. The plates also feature images of a stained-glass window and a cross.

McMaster argued the plates do not promote Christianity over other beliefs -- just as "Parrot Head" plates do not support Jimmy Buffet over fans of other singers.

"The plate is instead an accommodation to Christians, just as the other plates are accommodations to Parrot Heads and fraternity and sorority members," he said.

"The plate states, 'I Believe,' not 'We Believe,'" he added. "The plate is a personal statement of the motorist, not the state. Entanglement with religion is no more likely than entanglement with fraternities and sororities, musicians or nonprofits over the other plates permitted."

South Carolina remains the only state to approve the "I Believe" plates, Stevens said. Lt. Gov. Andre Bauer has said the idea came from Florida, but the proposal failed there.